1. Field of the Invention
The present invention relates to a sheet processing apparatus for processing sheets.
2. Description of Related Art
There are conventional image forming apparatuses such as copying machines including a sheet processing apparatus. For example, after images are formed on sheets, such sheet processing apparatus aligns or binds the sheets.
One such sheet processing apparatus executes an alignment process while supporting a sheet by an intermediate stacking tray and a pair of supporting portions. These supporting portions face each other and are arranged downstream of the intermediate stacking tray in a sheet conveyance direction. In addition, the supporting portions support side edges of the sheet in a width direction perpendicular to the sheet conveyance direction (see Japanese Patent Application Laid-Open No. 2006-306518 and Japanese Patent Application Laid-Open No. 2003-335450). However, according to the conventional techniques, it is difficult to stably align sheets having a long length (particularly, sheets having twice or more than twice the length of predetermined-size sheets) in the sheet conveyance direction perpendicular to the sheet width direction. Therefore, an apparatus capable of suitably aligning large-size sheets is demanded.